One of my great-grandfathers was born in England and migrated to Ireland.
Another was born in Moravia and migrated to Scotland, then to Ireland.
Their grandson, my father, migrated from Ireland to England.
I migrated from England to Germany.
My daughters both migrated back to England because they said (10 years ago) it was a nicer place to live. But both are now so totally revolted by the Brexit campaign that they are thinking of leaving, in one case making concrete plans.

Nigel Farage has a migrant wife; Gisela Stuart is a migrant; Priti Patel is the daughter of migrants. Boris's ancestry is so mixed he calls himself a one-man melting pot. And Winston Churchill had a migrant mother. What's sauce for the goose...

We all have migrant DNA from somewhere way (and some not so way) back to the 100 or so who are thought to have crossed from the Horn of Africa to Aden or thereabouts.

Does it matter? Yes, in a very few respects - some people of West Indian background carry a gene predisposing them to certain medical complaints for example - but it is how people allow themselves to mesh with where they end up which matters.

I do have blood going back to Denmark (?) via Normandy and almost certainly from Spain (from the Spanish emigration to Ireland) but before that is a big question. My "patron's" family fled France to Wales during the religeous wars but he was as English as you could ask for.